The present invention relates to a method for forming metal wire in semiconductor devices; and, more particularly, to a method for forming damascene type of copper wire in semiconductor devices.
With high integration of semiconductor devices, the reduction of design rule has been accelerated. So, the pitch of metal wire has been decreased. When the conventional metal wire process is applied to the formation of metal wire with high aspect ratio, it is difficult to obtain satisfactory results such as uniformity of critical dimension of metal wire, line etch profile and etch selectivity of photoresist. To improve the results, hard mask should be used. However, this results in the increase of fabrication cost and delay of device development.
Meanwhile, the damascene type of metal wire process is promising as a technique to solve the above-described problems and it is hopeful of applying to the fabrication of future generation ultra high-integrated devices.
The damascene type of metal wire process conventionally includes the steps of forming a trench for line and contact hole through an interlayer insulating layer, depositing barrier metal and metal wire, and removing the barrier metal and metal wire on the interlayer insulating layer by using chemical mechanical planarization (CMP).
In case of using copper as metal wire, the metal wire of copper has been conventionally formed by physical vapor deposition and electric plating method. Namely, the seed layer has been formed by physical vapor deposition and the trench for line and contact hole have been buried with copper by electric plating.
However, the step coverage of the seed layer deposited by physical vapor deposition is poor in this conventional method, so that voids may be formed within the contact hole or trench at the time of depositing copper by electric plating. The voids are very harmful in reliability of metal wire.
In consideration of this problem, forming the seed layer by chemical vapor deposition is to improve the step coverage to some extent. Nonetheless, there remains still a problem that the copper layer may be striped off because the orientation of copper layer deposited later by electric plating, its binding with the seed layer and the lower conductive layer are so poor.
It is, therefore, an object of the present invention to provide a method for forming damascene type of metal wire in a semiconductor device, which can improve the step coverage of seed layer in the metal wire process using copper and can also improve the orientation and binding force of the Cu CVD seed layer.
In accordance with an embodiment of the present invention, there is provided a method for forming damascene type of metal wire in a semiconductor device, the method comprising the steps of forming an interlayer-insulating layer over an entire structure including a predetermined lower conductive layer; patterning the interlayer-insulating layer to form a contact hole and trench for line; depositing a first copper layer along with the surface of the entire structure by physical vapor deposition; depositing a second copper layer for seed layer along with the surface of the first copper by chemical vapor deposition; forming a third copper layer for main wire by electric plating; and recessing the third, second and first copper layers until the interlayer insulating layer is exposed.
The present invention is to deposit a copper thin layer by physical vapor deposition, to form a seed layer by chemical vapor deposition, and then to deposit copper for main wire by electric plating, wherein the copper layer deposited by physical vapor deposition can increase the orientation and binding force of copper layer deposited later by CVD. The step coverage of the seed layer can be also improved due to chemical vapor deposition.